Re: [PATCH 1/2] lib/raid: use kmalloc() in calibrate_xor_blocks()

[David Laight <david.laight.linux@gmail.com>]

On Wed, 20 May 2026 11:17:51 +0300
"Mike Rapoport (Microsoft)" <rppt@kernel.org> wrote:

> The xor benchmark allocates an order 2 (4 pages) scratch buffer that is
> used purely as a CPU-only XOR working area.
> 
> For such large allocations kmalloc() would fall back to alloc_pages() but
> still kmalloc() is a better API as it does not require unnecessary
> castings and may provide more debugging possibilities.
> 
> Replace __get_free_pages() call with kmalloc().

You might want to use kvalloc() here.
It is less likely to fail.

-- David

> 
> Link: https://lore.kernel.org/all/635405e4-9423-4a25-a6e7-e03c8ea0bcbe@redhat.com
> Signed-off-by: Mike Rapoport (Microsoft) <rppt@kernel.org>
> ---
>  lib/raid/xor/xor-core.c | 5 +++--
>  1 file changed, 3 insertions(+), 2 deletions(-)
> 
> diff --git a/lib/raid/xor/xor-core.c b/lib/raid/xor/xor-core.c
> index bd4e6e434418..50931fbf0324 100644
> --- a/lib/raid/xor/xor-core.c
> +++ b/lib/raid/xor/xor-core.c
> @@ -8,6 +8,7 @@
>  
>  #include <linux/module.h>
>  #include <linux/gfp.h>
> +#include <linux/slab.h>
>  #include <linux/raid/xor.h>
>  #include <linux/jiffies.h>
>  #include <linux/preempt.h>
> @@ -114,7 +115,7 @@ static int __init calibrate_xor_blocks(void)
>  	if (forced_template)
>  		return 0;
>  
> -	b1 = (void *) __get_free_pages(GFP_KERNEL, 2);
> +	b1 = kmalloc(PAGE_SIZE * 4, GFP_KERNEL);
>  	if (!b1) {
>  		pr_warn("xor: Yikes!  No memory available.\n");
>  		return -ENOMEM;
> @@ -132,7 +133,7 @@ static int __init calibrate_xor_blocks(void)
>  	pr_info("xor: using function: %s (%d MB/sec)\n",
>  	       fastest->name, fastest->speed);
>  
> -	free_pages((unsigned long)b1, 2);
> +	kfree(b1);
>  	return 0;
>  }
>  
>